Actuator for the actuation of submarine devices

ABSTRACT

Submarine actuator for the actuation of a submarine device comprises a container body ( 2 ), from which a drive shaft ( 4 ) projects that is suitable for inserting in a seat of said submarine device, which through its rotation actuates said submarine device. Said shaft is moved by an electric motor ( 21, 22 ) arranged inside said container body and actuated by an electric control signal generated by a remote station.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to international application numberPCT/EP2005/000111, filed on Jan. 6, 2005, which claims priority toItalian application number MI2004A000022, filed on Jan. 13, 2004.

BACKGROUND

The present invention concerns an actuator for the actuation ofsubmarine devices, such as valves for closing and opening submarineducts.

Plants for transporting liquids and/or gases under the sea, for examplethe oil pipelines that run even for hundreds of meters under the sea,even at a depth of 3000 meters, comprise a plurality of intermediatestations in which valves for opening and closing the pipes or ducts thattransport such liquids or gases are foreseen.

Such valves are actuated by submarine actuators that determine theopening and closing of such valves transmitting a rotation movement tothe actuation shaft of the valve itself.

Such actuators are connected to the valves near to the submarinepipelines but must, however, be controlled from the surface or fromremote control stations (also submarine).

Actuators are known that are actuated manually by a robot associatedwith a submarine that reaches the place where the valve and the actuatorare situated and transmits the movement to the actuator itself throughthe robotized arm.

Hydraulic actuators are also known, which are actuated through ahydraulic station arranged at the surface having a hydraulic pipelinethat connects such a station at the surface to the submarine actuator.The pipeline transports the hydraulic energy, for example pressurizedoil, necessary for the actuation of the valve, on the bottom of the seawhere the actuator is situated.

The Applicant has observed that hydraulic type actuators require thepresence of an extremely large surface station of substantialenvironmental impact. Indeed, in such a station it is necessary togenerate the necessary hydraulic pressure to actuate the submarineactuator and, moreover, the hydraulic cable suitable for transferringthe hydraulic energy to the actuator must have substantial resistance toexternal pressure, since such actuators can be positioned intransportation plants even 3000 meters under the sea. All of this candetermine insufficient reliability of the valve and of the plant as awhole, since the cable that transports the hydraulic energy under thesea could be damaged and therefore could jeopardize the good operationof the valve.

On the other hand, actuators that can just be actuated manually requirethe use of a submarine to carry out the operation of changing the statusof the valve. Such an operation is both complex and expensive and doesnot allow the valve of the submarine transportation plant to becontrolled in real time from the surface.

The Applicant has set itself the problem of making the actuation fromthe surface or from a submarine control station of a valve applied to asubmarine pipeline reliable.

BRIEF DESCRIPTION OF SPECIFIC EMBODIMENTS

The Applicant has made a submarine actuator the movement of which iscarried out through at least one electric motor controlled by a remotecontrol station. The communication between the submarine actuator andthe station takes place by means of suitable electric cables, sized soas to withstand the external pressure that is present in the depths ofthe sea.

Moreover, the Applicant has made a system for controlling such anelectromechanical actuator, in which the actuation command of thecontrolled submarine device, for example a fluid transportation valve,can be sent from a control station independently to each electric motorpresent in the actuator.

An aspect of the present invention concerns a submarine actuator for theactuation of a submarine device comprising a container body from which adrive shaft extends that is suitable for inserting in a seat of saidsubmarine device and through its rotation for actuating said submarinedevice characterized in that said shaft is moved by at least oneelectric motor arranged inside said container body and actuated by anelectrical control signal generated by a control station.

BRIEF DESCRIPTION OF THE DRAWINGS

The characteristics and advantages of the actuator according to thepresent invention shall become clearer from the following description,given as an example and not for limiting purposes, of an embodiment withreference to the attached figures in which:

FIG. 1 is a front view of the actuator according to the presentinvention;

FIG. 2 is a section view along line A-A of FIG. 1 of the actuatoraccording to the present invention;

FIG. 3 is a side view of the actuator according to the presentinvention;

FIG. 4 schematically illustrates an example of an electronic controlboard of the actuator according to the present invention;

FIG. 5 schematically illustrates the main functions of the electroniccontrol board according to the present invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

With reference to the quoted figures the actuator according to thepresent invention is suitable for actuating a submarine device throughthe coupling of a drive shaft of said actuator in a suitable seat ofsaid submarine device. The submarine device to be actuated is, forexample, a valve for opening and closing a submarine pipeline.

The actuator according to the present invention comprises a containerbody formed from a substantially box-shaped element 2 and from asubstantially cylindrical element 3 made in a single body or connectedtogether.

From the base of said box-shaped element a drive shaft 4 projectsthrough which the movement is transmitted to the valve to be actuated.

Inside said box-shaped element at least one electric motor is arrangedsuitable for transmitting the movement to said drive shaft 4.

Moreover, the movement of said motor is controlled by a series ofelectronic control boards, which are inserted in said cylindricalelement 3.

In the example embodiment illustrated in the figures, the actuator,inside the box-shaped element, comprises two electric motors 21 and 22,each of which can separately control the rotation of said drive shaft 4,through the electronic control board.

The presence of two electric motors that can be controlled independentlyfrom each other allows the possibility of a lack of activation of thecommanded valve by the actuator to be minimized. Indeed, to block thecorrect operation of the valve it would be necessary for both of themotors to be shut down simultaneously.

The rotation of the drive shaft 4, able to be carried out independentlyby each of the motors, can, for example, be obtained through a gearmechanism, which comprises a transmission shaft 23, connected through apair of gears to the rotation shafts of the two electric motors 21 and22. On such a transmission shaft a worm screw 24 is provided, integralwith the rotation of said shaft, which engages with a further sprocket25 made on the extension of said drive shaft inside said box-shapedelement 2.

The box-shaped element 2 is preferably filled on the inside with alubricating liquid, for example a high-density insulating oil, and isprovided with a device for the compensation of the external pressurecomprising a pocket accumulator 6, firmly connected on a side of saidbox-shaped element that balances the internal pressure with the externalpressure through a separation membrane and connected to the actuator byan inlet pipeline 61.

Moreover, the drive shaft 4 completely crosses the box-shaped elementand, on its upper end 41 a visual recognition device of the positiontaken up by the valve commanded by the movement of the drive shaft 4 isforeseen. Moreover, on such an upper end of the drive shaft a seat isformed for the insertion of a possible robotized arm suitable forrotating the drive shaft in an emergency situation in which it is notpossible to actuate the drive shaft electrically. The cylindricalelement is a hermetic container into which a pressurized gas, forexample nitrogen, is inserted, which encloses the electronic controlboards for the motors inside it. The electrical connections between theelectronic control board and the motors are carried out by means ofelectric cables 7 connected to said cylindrical element and to saidbox-shaped element through connectors and hermetic through element.

An example of the electronic control board container in the actuatoraccording to the present invention is schematically illustrated in FIG.4. Such a board comprises a pilot circuit 31 or 32, a power supplycircuit 33 or 34 and a programmable logic unit 35 or 36 for each motor.

It is foreseen that there is, associated with the drive shaft 4 of theactuator, a transducer 26 of the position of such a shaft, which iselectrically connected with each programmable logic unit.

The parts of the control board inserted inside the cylindrical elementare in connection with the parts arranged inside the box-shaped elementthrough the electric cables 7, the connectors and/or the hermeticthrough elements 8.

The power supply of said electric motors can be carried out through asuitable power supply cable transported by the control station to thesubmarine actuator; alternatively, the electric power supply for saidmotors can be directly obtained from electric power supply linesassociated with the submarine transportation plant.

The control system of the electromechanical actuator according to thepresent invention is conveniently summarized in the block diagram ofFIG. 5, in which for each motor 21 or 22 (in the figures the controlsystem for the first motor 21 is illustrated), the quoted pilot circuit31, and the position transducer 26 and the functions that are carriedout by the programmable logic unit 35 comprising a positioning block 81that interfaces with the pilot circuit of the motor 31 (inverter), afiltering block 82 for a control signal of the actuator and a decodingblock 83 of the signal generated by the position transducer 26 areillustrated.

The actuator commands the opening and closing of the valve or of thesubmarine device with which it is associated through a control signalsent to a control input 84. The control signal is preferably filteredthrough such a filtering block 82 in order to limit possibleirregularities in the control signal.

The control signal SC can advantageously be of the on-off type or elseit can be a continuous signal that determines a regulation command forthe valve with linear displacements from 0% to 100%.

In particular, the filtered control signal SCF is obtained, havingmemorized a predetermined number N of prior input commands SCP fromwhich an average MCP (average of previous commands) has been worked outaccording to the following formula:

${SCF} = {\frac{\left\lbrack {\left( {{MCP}*N} \right) + {SC}} \right\rbrack}{N + 1}.}$

Moreover, the position signal of the valve or of the controlledsubmarine device is detected through the position transducer 26, whichgenerates a signal, for example typically a 4-20 mA signal, which isdecoded by said decoding block 83 and sent to the positioning block.

The decoding block carries out a comparison between the signal receivedand previous memorized signals corresponding to the open and closedlimit positions of the valve. From such a comparison and from subsequentprocessing, through a linearizing function, a precise and reliabledecoded position signal is obtained. The value of the transducer ismonitored constantly, in order to check its validity and correctoperation; indeed, an error of the transducer would result in a blockingof the positioning function and therefore a blocking of the command ofthe valve.

The positioning block functions 81 are substantially the core of thesystem and comprise the processing of the signals coming from theposition transducer 26 through the decoding block 83, from the controlinput 84 through the filtering block 82 and from the pilot circuit 31,in order to generate an activation signal of the electric motor 21.

Preferably, the processing consists of calculating a speed value anddirection SP for the rotation of the motor starting from the positionvalue of the valve to be reached SETP (open/closed) and from the currentposition of the valve POSA and sending a corresponding signal to thepilot circuit of the motor. For such a purpose, the positioning blockalso receives the value of the current absorbed by the motor from thepilot circuit, so as to be able to carry out a double retroactioncontrol both through the position transducer and through such absorptioncurrent of the motor.

Therefore, in short, the electronic control board comprises a firstretroaction circuit of the current absorbed by the motor between theprogrammable logic unit and the pilot circuit, and a second pilotcircuit of the position signal of the drive shaft between saidtransducer and said programmable logic unit.

The speed value can be calculated through the following formula:SP=√{square root over (SETP−POSA*KGAIN)}

Where KGAIN represents the gain of the positioning ring with referenceto the retroaction of the position transducer.

The calculated speed value is advantageously limited to a maximumpredetermined value, set based upon the displacement times that areintended to be carried out on the valve.

Moreover, the system foresees that it is possible to control the motorthrough an emergency control signal 85, which acts directly on the pilotcircuit 31 and therefore on the electrical actuation of the motoreliminating any control carried out by the programmable logic unit ofthe actuator. The actuator carries out the emergency maneuver when itreceives the aforementioned emergency control signal.

The actuator according to the present invention comprises at least twomotors, each of which can be controlled independently from the controlstation through the system described above in a master-slave typeconfiguration. This makes it possible, in the case in which there is analarm on a motor, or on an electronic control board of the motor, forthe system to automatically take care of switching the command onto theother motor of the actuator.

1. A method, comprising: pneumatically pressurizing a control circuit ina first enclosure portion of a submersible actuator, wherein the firstenclosure portion is hermetically sealed, and wherein pneumaticallypressurizing comprises inertly pressurizing the control circuit in thefirst enclosure portion with pressurized nitrogen; and hydraulicallypressurizing at least one electric motor in a second enclosure portionof the submersible actuator, wherein the control circuit is coupled tothe at least one electric motor.
 2. The method of claim 1, comprisingreceiving an electrical control signal from a remote control station,processing the electrical control signal in the control circuit, andtriggering the electric motor to actuate a submerged flow controlmechanism.
 3. The method of claim 1, wherein the at least one electricmotor comprises first and second electric motors, and the method furthercomprises independently controlling the first and second electric motorsto enable independent actuation of a submerged flow control mechanism.4. The method of claim 1, comprising controlling the submersibleactuator based on a target position, feedback, and historical dataassociated with the submersible actuator.
 5. The method of claim 1,comprising controlling a speed value and a direction for rotation of theat least one electric motor based on a target shaft position and acurrent shaft position sensed by a position sensor.
 6. The method ofclaim 1, comprising controlling the submersible actuator based on afirst feedback indicative of an actuator position and a second feedbackindicative of an absorbed current.
 7. The method of claim 1, wherein thefirst and second enclosure portions are capable of withstandingpressures at up to 3,000 meters of sea depth.
 8. A system, comprising: asubmersible actuator, comprising: a first container filled with aliquid; a second container filled with nitrogen; an electric motordisposed in the first container; and a control circuit disposed in thesecond container, wherein the second container is hermetically sealed,and wherein the control circuit is configured to control the electricmotor to actuate a submarine device.
 9. The system of claim 8, whereinthe submersible actuator comprises a worm gear coupled to the electricmotor.
 10. The system of claim 8, wherein the control circuit isconfigured to adjust a speed of the electric motor based on a currentposition and a target position of the submarine device.
 11. The systemof claim 8, wherein the control circuit is configured to control theelectric motor based on historical data associated with the actuation ofthe submarine device.
 12. The system of claim 8, wherein the controlcircuit is configured to control the electric motor based on feedbackindicative of a current absorbed by the electric motor.
 13. The systemof claim 8, comprising a visual recognition device and a robot interfacecoupled to the submersible actuator, wherein the visual recognitiondevice enables viewing of an actuation position associated with thesubmarine device, and the robot interface enables a robot to control thesubmersible actuator.
 14. The system of claim 8, wherein the first andsecond containers are capable of withstanding pressures at up to 3,000meters of sea depth.
 15. A system, comprising: a submersible actuator,comprising: a first housing having an electric motor disposed in a firstpressurized fluid, wherein the first pressurized fluid is a pressurizedlubricating liquid; and a second housing having a control circuitdisposed in a second pressurized fluid, wherein the second housing ishermetically sealed, wherein the second pressurized fluid is nitrogen,and wherein the control circuit is coupled to the electric motor, andthe control circuit is configured to communicate with a remote controlstation.
 16. The system of claim 15, wherein the control circuit isconfigured to compare a value of a control signal with an average of apredetermined number of previous control signals.
 17. The system ofclaim 15, comprising a membrane accumulator coupled to the submersibleactuator and configured to balance internal and external pressures. 18.The system of claim 15, wherein the control circuit is configured tocontrol the electric motor based on feedback indicative of a currentabsorbed by the electric motor.
 19. The system of claim 15, comprising aflow control mechanism coupled to the submersible actuator.
 20. Thesystem of claim 15, wherein the control circuit is configured to controla speed value and a direction for rotation of the electric motor basedon a target shaft position and a current shaft position sensed by aposition sensor.
 21. The system of claim 15, wherein the first andsecond housings are capable of withstanding pressures at up to 3,000meters of sea depth.
 22. The system of claim 15, wherein the submersibleactuator comprises another electric motor coupled to the controlcircuit, and the control circuit is configured to control the electricmotors independent from one another.
 23. The system of claim 22, whereinthe electric motors are independently drivingly coupled to a drive shaftvia a transmission, wherein the transmission comprises a transmissionshaft, a worm screw coupled to the transmission shaft, and a sprocketcoupled to the worm screw and the drive shaft, wherein the electricmotors are coupled to the transmission shaft.